During some rapid prototyping processes, such as stereolithography, it is common to perform a step removing uncured and partially-cured residual resin from formed objects using a solvent such as Tripropylene Glycol Methyl Ether, which is also referred to as Glycol Ether TPM, or just TPM. This step is typically performed to remove uncured resin that coats an object after the object has been formed and to remove undesired partially-cured resin therefrom, prior to performing an additional step of “baking” the part with ultraviolet light to fully cure all resin remaining in the part.
Typically, the step of removing resin from objects comprises submersing the formed objects in a bath of solvent for a period of time. During this step, an agitator is often provided in the bath of solvent to create relative movement between the objects and the solvent.
As the bath of solvent is utilized to remove resin from objects, the concentration level of dissolved resin in the solvent bath increases. Eventually, the solvent becomes fully saturated with dissolved resin, and thereby becomes ineffective in removing further resin from objects. Once it is determined that solvent has become saturated, the bath of solvent is typically fully or partially drained, and then resupplied with fresh solvent.
Determining when a bath of solvent has become saturated or predicting how soon such a bath of solvent will become saturated has been difficult. Resort is often made to empirical data as a guide for determining when to service a bath solvent. However, such data is often inaccurate or unreliable and, as a result, solvent is often stocked in reserve. Additionally, the unpredictable timing of the solvent's saturation results in unexpected service delays that increase production periods and disrupt schedules associated with the production of resin cured objects.